// Copyright 2019-2024 ChainSafe Systems
// SPDX-License-Identifier: Apache-2.0, MIT

//! # Differences between serializers
//!
//! The serializer created here uses `multihash` and `libipld-json` uses plain
//! `base64`. That means one has an extra `m` in front of all the encoded byte
//! values, using our serializer.
//!
//! For example:
//!
//! this:
//! `{ "/": { "bytes": "mVGhlIHF1aQ" } }`
//!
//! `libipld-json`:
//! `{ "/": { "bytes": "VGhlIHF1aQ" } }`
//!
//! Since `Lotus` is also using `multihash-base64` and we're trying to be
//! compatible, we cannot switch to `libipld-json`.
//!
//! # Tech debt
//! - The real way to do this is to implement [`libipld::codec`] bits appropriately,
//!   or embrace using our own struct.

use std::{collections::BTreeMap, fmt};

use super::*;

use ::cid::multibase;
use libipld::{ipld, Ipld};
use serde::de;

#[derive(Serialize, Deserialize, JsonSchema)]
#[schemars(rename = "Ipld")]
pub struct IpldLotusJson(
    #[serde(with = "self")]
    #[schemars(with = "serde_json::Value")] // opt-out of JsonSchema for now
    Ipld,
);

impl HasLotusJson for Ipld {
    type LotusJson = IpldLotusJson;
    #[cfg(test)]
    fn snapshots() -> Vec<(serde_json::Value, Self)> {
        vec![
            (
                json!({
                    "my_link": {
                        "/": "QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n"
                    },
                    "my_bytes": {
                        "/": { "bytes": "mVGhlIHF1aQ" }
                    },
                    "my_string": "Some data",
                    "my_float": {
                        "/": { "float": "10.5" }
                    },
                    "my_int": {
                        "/": { "int": "8" }
                    },
                    "my_neg_int": {
                        "/": { "int": "-20" }
                    },
                    "my_null": null,
                    "my_list": [
                        null,
                        { "/": "bafy2bzaceaa466o2jfc4g4ggrmtf55ygigvkmxvkr5mvhy4qbwlxetbmlkqjk" },
                        {"/": { "int": "1" }},
                    ]
                }),
                ipld!({
                    "my_link": Ipld::Link("QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n".parse().unwrap()),
                    "my_bytes": Ipld::Bytes(vec![0x54, 0x68, 0x65, 0x20, 0x71, 0x75, 0x69]),
                    "my_string": "Some data",
                    "my_float": 10.5,
                    "my_int": 8,
                    "my_neg_int": -20,
                    "my_null": null,
                    "my_list": [
                        null,
                        Ipld::Link("bafy2bzaceaa466o2jfc4g4ggrmtf55ygigvkmxvkr5mvhy4qbwlxetbmlkqjk".parse().unwrap()),
                        1,
                    ],
                }),
            ),
            // Test ported from go-ipld-prime (making sure edge case is handled)
            (
                json!({"/":{"/":"QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n"}}),
                ipld!({"/": Ipld::Link("QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n".parse().unwrap())}),
            ),
        ]
    }
    fn into_lotus_json(self) -> Self::LotusJson {
        IpldLotusJson(self)
    }
    fn from_lotus_json(IpldLotusJson(it): Self::LotusJson) -> Self {
        it
    }
}

const BYTES_JSON_KEY: &str = "bytes";
const INT_JSON_KEY: &str = "int";
const FLOAT_JSON_KEY: &str = "float";

/// Wrapper for serializing a IPLD reference to JSON.
#[derive(Serialize)]
#[serde(transparent)]
struct Ref<'a>(#[serde(with = "self")] pub &'a Ipld);

fn serialize<S>(ipld: &Ipld, serializer: S) -> Result<S::Ok, S::Error>
where
    S: Serializer,
{
    match &ipld {
        Ipld::Null => serializer.serialize_none(),
        Ipld::Bool(bool) => serializer.serialize_bool(*bool),
        Ipld::Integer(i128) => serialize(
            &ipld!({ "/": { INT_JSON_KEY: i128.to_string() } }),
            serializer,
        ),
        Ipld::Float(f64) => serialize(
            &ipld!({ "/": { FLOAT_JSON_KEY: f64.to_string() } }),
            serializer,
        ),
        Ipld::String(string) => serializer.serialize_str(string),
        Ipld::Bytes(bytes) => serialize(
            &ipld!({ "/": { BYTES_JSON_KEY: multibase::encode(multibase::Base::Base64, bytes) } }),
            serializer,
        ),
        Ipld::List(list) => {
            let wrapped = list.iter().map(Ref);
            serializer.collect_seq(wrapped)
        }
        Ipld::Map(map) => {
            let wrapped = map.iter().map(|(key, ipld)| (key, Ref(ipld)));
            serializer.collect_map(wrapped)
        }
        Ipld::Link(cid) => serialize(&ipld!({ "/": cid.to_string() }), serializer),
    }
}

fn deserialize<'de, D>(deserializer: D) -> Result<Ipld, D::Error>
where
    D: Deserializer<'de>,
{
    deserializer.deserialize_any(JSONVisitor)
}

/// JSON visitor for generating IPLD from JSON
struct JSONVisitor;
impl<'de> de::Visitor<'de> for JSONVisitor {
    type Value = Ipld;

    fn expecting(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.write_str("any valid JSON value")
    }

    #[inline]
    fn visit_str<E: de::Error>(self, value: &str) -> Result<Self::Value, E> {
        self.visit_string(String::from(value))
    }

    #[inline]
    fn visit_string<E: de::Error>(self, value: String) -> Result<Self::Value, E> {
        Ok(Ipld::String(value))
    }
    #[inline]
    fn visit_bytes<E: de::Error>(self, v: &[u8]) -> Result<Self::Value, E> {
        self.visit_byte_buf(v.to_owned())
    }

    #[inline]
    fn visit_byte_buf<E: de::Error>(self, v: Vec<u8>) -> Result<Self::Value, E> {
        Ok(Ipld::Bytes(v))
    }

    #[inline]
    fn visit_u64<E: de::Error>(self, v: u64) -> Result<Self::Value, E> {
        Ok(Ipld::Integer(v.into()))
    }

    #[inline]
    fn visit_i64<E: de::Error>(self, v: i64) -> Result<Self::Value, E> {
        Ok(Ipld::Integer(v.into()))
    }

    #[inline]
    fn visit_i128<E: de::Error>(self, v: i128) -> Result<Self::Value, E> {
        Ok(Ipld::Integer(v))
    }

    #[inline]
    fn visit_bool<E: de::Error>(self, v: bool) -> Result<Self::Value, E> {
        Ok(Ipld::Bool(v))
    }

    #[inline]
    fn visit_none<E: de::Error>(self) -> Result<Self::Value, E> {
        self.visit_unit()
    }

    #[inline]
    fn visit_unit<E: de::Error>(self) -> Result<Self::Value, E> {
        Ok(Ipld::Null)
    }

    #[inline]
    fn visit_seq<V: de::SeqAccess<'de>>(self, mut visitor: V) -> Result<Self::Value, V::Error> {
        let mut vec = Vec::new();

        while let Some(IpldLotusJson(elem)) = visitor.next_element()? {
            vec.push(elem);
        }

        Ok(Ipld::List(vec))
    }

    #[inline]
    fn visit_map<V>(self, mut visitor: V) -> Result<Self::Value, V::Error>
    where
        V: de::MapAccess<'de>,
    {
        let mut map = BTreeMap::new();

        while let Some((key, IpldLotusJson(value))) = visitor.next_entry()? {
            map.insert(key, value);
        }

        if map.len() == 1 {
            if let Some(v) = map.get("/") {
                match v {
                    Ipld::String(s) => {
                        // { "/": ".." } Json block is a Cid
                        return Ok(Ipld::Link(s.parse().map_err(de::Error::custom)?));
                    }
                    Ipld::Map(obj) => {
                        if let Some(Ipld::String(s)) = obj.get(BYTES_JSON_KEY) {
                            // { "/": { "bytes": "<multibase>" } } Json block are bytes encoded
                            let (_, bz) = multibase::decode(s)
                                .map_err(|e| de::Error::custom(e.to_string()))?;
                            return Ok(Ipld::Bytes(bz));
                        }
                        if let Some(Ipld::String(s)) = obj.get(INT_JSON_KEY) {
                            // { "/": { "int": "i128" } }
                            let s = s
                                .parse::<i128>()
                                .map_err(|e| de::Error::custom(e.to_string()))?;
                            return Ok(Ipld::Integer(s));
                        }
                        if let Some(Ipld::String(s)) = obj.get(FLOAT_JSON_KEY) {
                            // { "/": { "float": "f64" } }
                            let s = s
                                .parse::<f64>()
                                .map_err(|e| de::Error::custom(e.to_string()))?;
                            return Ok(Ipld::Float(s));
                        }
                    }
                    _ => (),
                }
            }
        }

        Ok(Ipld::Map(map))
    }

    #[inline]
    fn visit_f64<E: de::Error>(self, v: f64) -> Result<Self::Value, E> {
        Ok(Ipld::Float(v))
    }
}

#[test]
fn snapshots() {
    assert_all_snapshots::<Ipld>()
}

#[cfg(test)]
quickcheck::quickcheck! {
    fn quickcheck(val: Ipld) -> () {
        let mut val = val;
        /// `NaN != NaN`, which breaks our round-trip tests.
        /// Correct this by changing any `NaN`s to zero.
        fn fixup_floats(ipld: &mut Ipld) {
            match ipld {
                Ipld::Float(v) => {
                    if v.is_nan() {
                        *ipld = Ipld::Float(0.0);
                    }
                }
                Ipld::List(list) => {
                    for item in list {
                        fixup_floats(item);
                    }
                }
                Ipld::Map(map) => {
                    for item in map.values_mut() {
                        fixup_floats(item);
                    }
                }
                _ => {}
            }
        }
        fixup_floats(&mut val);
        assert_unchanged_via_json(val)
    }
}

/// [`quickcheck`] [found a round-trip bug in CI][failing job], tracked by [#3383][issue]
///
/// ```text
/// thread 'ipld::json::tests::ipld_roundtrip' panicked at '[quickcheck] TEST FAILED (runtime error).
/// Arguments: ([[{"": {"": [[[{"": [{"": [{"": [{"": [[{"": [[{"": {"/": ""}}]]}]]}]}]}]}]]]}}]])
/// Error: "called `Result::unwrap()` on an `Err` value: Error(\"Input too short\", line: 1, column: 52)"',
/// ```
/// The actual error message is a little ambiguous with regards to the cause
/// because [`libipld` has a custom debug implementation][unhelpful]
///
/// Here's what the minimal test case (or simply another bug) is after trying to understand the above.
///
/// [issue]: https://github.com/ChainSafe/forest/issues/3383
/// [failing job]: https://github.com/ChainSafe/forest/actions/runs/5877726416/job/15938386821?pr=3382#step:9:1835
/// [unhelpful]: https://github.com/ipld/libipld/blob/8478d6d66576636b9970cb3b00a232be7a88ea42/core/src/ipld.rs#L53-L63
#[test]
#[should_panic = "Input too short"]
fn issue_3383() {
    let poison = Ipld::Map(BTreeMap::from_iter([(
        String::from("/"),
        Ipld::String(String::from("")),
    )]));
    let serialized = serde_json::to_value(Ref(&poison)).unwrap();

    // we try and parse the map as a CID, even though it's meant to be a map...
    let IpldLotusJson(round_tripped) = serde_json::from_value(serialized).unwrap();

    pretty_assertions::assert_eq!(round_tripped, poison); // we never make it here
}